Polyamide, preparation process therefor and uses thereof

ABSTRACT

The present disclosure relates to a novel polyamide synthesized from biobased monomers. The novel polyamide comprises the repeating unit of formula I, described herein, in which R represents a covalent bond or a divalent hydrocarbon-based group chosen from saturated or unsaturated aliphatics, saturated or unsaturated cycloaliphatics, aromatics, arylaliphatics and alkylaromatics. The present disclosure also relates to a process for preparing the said polyamide, to its uses, and to articles and compositions comprising the said polyamide.

This application is a continuation of U.S. application Ser. No.14/416,935, filed Jan. 23, 2015 know U.S. Pat. No. 9,670,319), which isa U.S. national phase entry under 35 U.S.C. § 371 of InternationalApplication No. PCT/EP2013/064581, filed on Jul. 10, 2013, which claimsthe priority of International Application No. PCT/CN2012/078918, filedon Jul. 20, 2012. The entire contents of these applications are beingincorporated herein by reference for all purposes.

The present invention relates to a novel polyamide, to a process forpreparing it and to its uses. The invention more particularly relates toa polyamide synthesized from biobased monomers.

The term “biobased” means that the material in question is derived fromrenewable resources. A renewable resource is a natural—animal orplant—resource whose stock can be reconstituted over a short period on ahuman timescale. It is in particular necessary for this stock to be ableto be renewed as quickly as it is consumed.

Unlike materials derived from fossil materials, renewable startingmaterials contain a large proportion of ¹⁴C. This characteristic mayespecially be determined via one of the methods described in standardASTM D6866, especially according to the mass spectrometry method or theliquid scintillation spectrometry method.

These renewable resources are generally produced from cultivated ornon-cultivated vegetable matter such as trees, plants such as sugarcane,corn, cassava, wheat, rapeseed, sunflower, palm, castor-oil plant or thelike, or from animal matter such as fats (tallow, etc.).

Polymers synthesized from biobased monomers are of major interestnowadays since they make it possible to reduce the environmentalfootprint. There are a large number of combinations of biobased monomersor of combinations of monomers that are biobased and derived from fossilresources, which may be used to generate polymers that are then termedbiobased. Some of these biobased polymers may be used to replacepolymers derived from fossil resources. This is the case, for example,for polyamide PA 6.10, synthesized from hexamethylenediamine (fossilresource) and from biobased sebacic acid derived from castor oil, whichcan replace PA 12 (derived from fossil resources) especially in motorvehicle applications.

Among the biobased monomers, there is great interest in2,5-furandicarboxylic acid, obtained, for example, fromhydroxymethylfurfural (HMF), which is itself obtained, for example, fromsugars, such as glucose.

2,5-Furandicarboxylic acid is especially used in direct replacement forterephthalic acid, derived from fossil resources, and in combinationwith diols such as ethylene glycol, 1,3-propanediol or 1,4-butanediol,to synthesize semi-crystalline polyesters that have excellentproperties, whether for wrapping or textile applications. Thus,polyethylene furanoate (PEF) may be used instead of polyethyleneterephthalate (PET) for the production of bottles.

Industrially, polyesters of the PET type are mainly synthesized via adirect esterification route between terephthalic acid and diols.

However, modifications of these industrial units prove to be necessaryin order to synthesize high-quality PEFs, since, in the course of thisreaction, the 2,5-furandicarboxylic acid degrades into furan, which is atoxic, carcinogenic and flammable molecule.

It is therefore more judicious to perform the synthesis of PEFsaccording to another industrial route for the manufacture of PETs fromdimethyl terephthalates. When applied to PEFs, this “diester” route isthe reaction between dimethyl 2,5-furanoate and an excess of diol, theexcess of diol being removed by distillation under vacuum to make thepolyester chains grow.

Semi-crystalline polyamides such as PA 66, PA 6, PA 11, PA 12 and PA 46or polyphthalamides PA 6T/66, PA 6T/MT and PA 6T/6I, PA 10T and PA 9Tare technical polymers that are widely used in applications such asmotor vehicles, textiles or in the electrical and electronics (E&E)sector. They constitute the vast majority of the polyamides soldworldwide. Amorphous polyamides are, for their part, more marginal sincethe amorphous nature often limits the application performances and theworking temperature range.

Polyamides have also been synthesized from 2,5-furandicarboxylic acidespecially for the purpose of replacing terephthalic acid with abiobased monomer. In contrast with polyesters derived from2,5-furandicarboxylic acid, it appears, from a recent study by UlrichFehrenbacher published in Chemie Ingenieur Technik (Polymere) 2009, 81,11, 1829-1835, that the polyamides made from the methyl diesterderivative of 2,5-furandicarboxylic acid and from biobased commercialdiamines (e.g. 1,10-diaminodecane) or derived from fossil resources(e.g. hexamethylenediamine or 1,12-diaminododecane) are amorphous.

This characteristic represents a curb on the development of polyamidesfrom 2,5-furandicarboxylic acid, since they cannot replace thesemi-crystalline polyamides derived from fossil resources.

Furthermore, as for polyesters, the use of 2,5-furandicarboxylic acidfor polyamide manufacture should be avoided since it generates furan,which is toxic.

Another curb on the development of these polyamides is the recourse to a“diester aminolysis” process, i.e. a process that consists in reacting adiamine with a diester. Specifically, such a process has two majordrawbacks, in contrast with the case of the polyesters synthesized viathe “diester” route. The first drawback is the appearance of sidereactions that have an impact on the thermal properties (for example thecrystallization) of the polyamides. The second drawback is that it isnecessary to work with a stoichiometric amount of diamine and of diesterin order to obtain polyamides of high molar masses. However, it isdifficult to control this stoichiometric amount of diamine and ofdiester from an industrial point of view.

There is thus still a need to propose novel polyamides, which arepreferably semi-crystalline, derived from biobased molecules, which canreplace the polyamides derived from fossil resources.

Furthermore, there is also a need to find a synthetic route for thesebiobased polyamides that is simple, clean and reproducible and thatadvantageously uses the industrial equipment already in place forstandard polyamides such as polyamide 66. Furthermore, the manufacturingprocess for synthesizing these polyamides should advantageously make itpossible to achieve high molar masses.

In this context, it has been discovered, entirely surprisingly, thatdiacids or derivatives which contain a tetrahydrofuran ring make itpossible, especially in combination with diamines, to synthesize novelpolyamides that have particularly advantageous properties in the usualapplications of polyamides. These diacids or derivatives, which areadvantageously biobased, may be obtained especially from biobased2,5-furandicarboxylic acid.

One subject of the invention is thus a novel polyamide comprising therepeating unit of formula I below:

-   -   in which    -   R represents a covalent bond or a divalent hydrocarbon-based        group chosen from saturated or unsaturated aliphatics, saturated        or unsaturated cycloaliphatics, aromatics, arylaliphatics and        alkylaromatics.

A subject of the invention is also a process for preparing the polyamideof the invention, which comprises a polycondensation reaction between:

-   -   at least one dicarboxylic acid or at least one carboxylic acid        diester or at least one dinitrile or at least one acyl        dichloride of respective formulae IV, IV′, IV″ and IV′″ below:

where R₁ and R₂, which are identical or different, are C1-C4 alkyls;

and

at least one diamine of formula V below:H₂N—R—NH₂  (V)

with R as defined above.

Furthermore, a subject of the invention is the use of the polyamide ofthe invention for preparing articles by moulding, injection moulding,injection/blow-moulding, extrusion/blow-moulding, extrusion or spinning.The present invention is thus also directed towards articles obtainedfrom the polyamide according to the invention, the said articles beingable to take the form of moulded or extruded pieces, yarns, fibres,filaments or films.

The articles thus obtained have applications in numerous fields such astechnical plastics (motor vehicle, E&E, consumer goods, etc.),industrial yarns, the textile industry, packaging, etc.

The present invention also relates to compositions comprising at leastthe polyamide of the invention and optionally reinforcing fillers and/orvarious additives.

The novel polyamide according to the invention comprises a repeatingunit of formula I as described above in which R represents a covalentbond or a divalent hydrocarbon-based group chosen from saturated orunsaturated aliphatics, saturated or unsaturated cycloaliphatics,aromatics, arylaliphatics and alkylaromatics.

The term “saturated aliphatic group” means, for example, linear orbranched alkyl groups having from 1 to 36 carbon atoms. Preferably, alinear alkyl group having from 4 to 14 carbon atoms will be chosen.

The term “unsaturated aliphatic group” means, for example, that theinvention does not exclude the presence of an unsaturation on thealiphatic hydrocarbon-based chain, such as one or more double bonds thatmay or may not be conjugated, or alternatively a triple bond.

The hydrocarbon-based chain of the above aliphatic groups may optionallybe interrupted with a heteroatom (for example oxygen, nitrogen,phosphorus or sulphur) or a functional group (for example carbonyl) ormay bear one or more substituents (for example hydroxyl or sulphone)provided that they do not interfere under the reaction conditions orwith regard to the intended application.

As preferred examples for the aliphatic groups R, mention may be made ofthe following groups: —(CH₂)₄—, —(CH₂)₅—, —(CH₂)₆—,—(CH₂)—CH(CH₃)—(CH₂)₃—, —(CH₂)₁₀— and —(CH₂)₁₂—.

In formula (I), R may also represent a cycloaliphatic (or carbocyclic)group, which is preferably monocyclic or bicyclic. The number of carbonatoms in each ring may range from 4 to 8 carbon atoms, but it ispreferably equal to 4, 5 or 6 carbon atoms. The carbocycle may besaturated or may comprise 1 or 2 unsaturations in the ring, preferably 1to 2 double bonds.

As preferred examples of carbocyclic and monocyclic groups for A,mention may be made of the 1,4-cyclohexyl or 1,3-cyclohexyl group,preferably the trans stereoisomer or else the4,4′-methylenebis(cyclohexyl) group.

In other advantageous embodiments of the invention, R may also representan aromatic divalent hydrocarbon-based group comprising, advantageously,at least 5 carbon atoms in its aromatic ring, which may be interruptedwith a heteroatom such as a nitrogen atom. Preferably, the divalentaromatic hydrocarbon-based group comprises from 6 to 18 carbon atoms,such as a 1,4-benzene, 1,3-benzene or 2,6-naphthalene group. It may alsobe a divalent alkylaromatic hydrocarbon-based group such as1,4-phenylene-2,5-dimethyl, or a divalent arylaliphatichydrocarbon-based group such as the group —(CH₂)_(n)-Ph-(CH₂)_(n)— withn and n′ being integers advantageously between 1 and 4 and the positionsof the —(CH2)n- groups are 1.3 and 1.4. As preferred examples for thearomatic groups R, a 1,4-benzene, 1,3-benzene or —(CH₂)-Ph-(CH₂)— groupin positions 1.3 and 1.4 will be chosen.

According to one particular embodiment of the invention, R is a divalenthydrocarbon-based group that is biobased in the sense of the presentinvention (standard ASTM D6866).

According to one preferred embodiment of the invention, the polyamide ofthe invention has a true number-average molar mass Mn of between 500 and50 000 g/mol, preferably between 2000 and 30 000 g/mol and even morepreferentially between 5000 and 25 000 g/mol.

The true number-average molar masses are determined by various knownmethods such as gel permeation chromatography. The term “truenumber-average molar masses” should be understood as meaning that theyare not measurements as polystyrene equivalents.

According to a first advantageous embodiment, the polyamide according tothe invention predominantly comprises the repeating unit of formula I.This repeating unit of formula I is advantageously derived from thepolycondensation reaction between a dicarboxylic acid monomer of formulaIV as defined above and a diamine monomer of formula V: H₂N—R—NH₂ (V)with R as defined above. As explained previously, the dicarboxylic acidmay also be substituted with a corresponding methyl, ethyl, propyl orbutyl diester (formula IV′) or alternatively with a correspondingdinitrile (formula IV″), or alternatively an acyl chloride (formulaIV′″).

The term “predominantly” means that the polyamide may be a homopolyamideconsisting entirely of the repeating unit of formula I, but also that itmay be a copolymer comprising other repeating units different from theunit of formula I, these repeating units possibly being derived fromcomonomers such as other dicarboxylic acids, other diamines, amino acidsand/or lactams. These comonomers may represent up to 50 mol %,preferably up to 30 mol % and even more preferentially up to 15 mol % ofthe total amount of monomers introduced for the preparation of thepolyamide of the invention.

According to a second advantageous embodiment, the polyamide accordingto the invention comprises to a minor extent the repeating unit offormula I. This repeating unit of formula I is advantageously derivedfrom the polycondensation reaction between a dicarboxylic acid monomerof formula IV as defined above and a diamine monomer of formula V:H₂N—R—NH₂ (V) with R as defined above. As explained previously, thedicarboxylic acid may also be substituted with a corresponding methyl,ethyl, propyl or butyl diester (formula IV′) or alternatively with acorresponding dinitrile (formula IV″), or alternatively an acyl chloride(formula IV′″).

The term “to a minor extent” means that the polyamide is a copolymercomprising other repeating units different from the unit of formula I,these repeating units possibly being derived from monomers such as otherdicarboxylic acids, other diamines, amino acids and/or lactams. Theseother monomers may in that case represent up to 95 mol %, preferably upto 70 mol %, of the total amount of monomers introduced for thepreparation of the polyamide of the invention. In other words, theprecursor monomers of the repeating unit of formula I may in that caserepresent up to 5 mol %, preferably up to 30 mol %, of the total amountof monomers introduced for the preparation of the polyamide of theinvention. The copolymer in question may be, for example, PA 6T/6TF,PA10T/10TF, PA6T/6TF/66, PA66/6TF, PA12T/12TF and PA610/6TF, in theproportions described above.

Copolymer of the present invention may be chosen in group consisting of:PA 6T/6TF, PA10T/10TF, PA6T/6TF/66, PA66/6TF, PA12T/12TF and PA610/6TF.

The dicarboxylic acid monomers of formula IV, diester monomers offormula IV′, dinitrile monomers of formula IV″ and acyl dichloridemonomers of formula IV′″ may be the cis or trans stereoisomers or amixture thereof. Preferably, the trans stereoisomer will be chosen. Forthe cis stereoisomer, the chiral carbons in positions 2 and 5 may be R,Sor S,R or a meso mixture. For the trans stereoisomer, the chiral carbonsin positions 2 and 5 may be S,S or R,R or the racemic mixture.

The diacids of formula IV, which are advantageously biobased, may besynthesized, for example, by catalytic hydrogenation, for example withRaney nickel, from 2,5-furandicarboxylic acid (FDCA) or the methyldiester of that acid, followed by a hydrolysis.

The diesters of formula IV′, which advantageously are biobased, may besynthesized, for example, by esterification of THFDCA (diacid of formulaIV) with a monoalcohol such as methanol, ethanol, propanol or butanol orby esterification of FDCA with a monoalcohol such as methanol, ethanol,propanol or butanol, followed by catalytic hydrogenation, for examplewith Raney nickel.

The dinitriles of formula IV″, which advantageously are biobased, may besynthesized, for example, by nitrilation of THFDCA (diacid of formulaIV) with ammonia.

The acyl dichlorides of formula IV′″, which advantageously are biobased,may be obtained, for example, from the reaction of THFDCA (diacid offormula IV) with thionyl chloride.

The processes for obtaining these various monomers are conventionalprocesses which are known to a person skilled in the art.

These monomers are particularly advantageous because they are able toconfer a semi-crystalline character on the polyamides of the invention.

The diamine monomers of formula V are advantageously chosen from:hexamethylenediamine; 1,4-diaminobutane; 1,5-diaminopentane;2-methyl-1,5-diaminopentane; 2-methylhexamethylenediamine;3-methylhexamethylenediamine; 2,5-dimethylhexamethylenediamine;2,2-dimethylpentamethylenediamine; 1,7-diaminoheptane,1,8-diaminooctane; 1,9-diaminononanediamine; 2-methyl-1,8-octanediamine,5-methylnonanediamine, 1,10-diaminodecane; 1,11-diaminoundecane;1,12-diaminododecane; 2,2,4- and 2,4,4-trimethylhexamethylenediamine;2,2,7,7-tetramethyloctamethylenediamine; meta-xylylenediamine;para-xylylenediamine; isophoronediamine; 4,4′-diaminodiphenylmethane;4,4′-methylenebis-(cyclohexylamine); 1,3-bis(aminomethyl) cyclohexane;C2-C16 aliphatic diamines that may be substituted with one or more alkylgroups, the C36 diamines originating from fatty acid dimers known underthe name Priamine; 2,5-bis(aminomethyl)furan and2,5-bis(aminomethyl)tetrahydrofuran; para-phenylenediamine;meta-phenylenediamine; and the ethoxylated diamines known under the nameJeffamine or Elastamine (polyetherdiamine comprising ethers of ethyleneglycol and/or of propylene glycol and/or of tetramethylene glycol).

The majority of these monomers are commercially available and may bebiobased. These monomers are particularly advantageous because they areable to confer a semi-crystalline character on the polyamides of theinvention.

The diamine monomers of formula V may be chosen from2,5-bis(aminomethyl)furan and 2,5-bis(aminomethyl)tetrahydrofuran. Inthe particular embodiment in which the diamine monomer of formula V is2,5-bis(aminomethyl)tetrahydrofuran, the compound in question may be thecis or trans stereoisomer or a mixture thereof.

These advantageously biobased diamines may be synthesized, for examplefor 2,5-bis(aminomethyl)furan, by nitrilation of 2,5-furandicarboxylicacid followed by a selective hydrogenation, and a hydrogenation of thefuran ring of 2,5-bis(aminomethyl)furan to prepare2,5-bis(aminomethyl)tetrahydrofuran.

Dicarboxylic acid comonomers that may be used according to theinvention, may be, for example, oxalic acid, glutaric acid, adipic acid,suberic acid, azelaic acid, sebacic acid, 1,12-dodecanedioic acid; 1,3-or 1,4-cyclohexanedicarboxylic acid; 1,3- or 1,4-phenylenediacetic acid;1,3- or 1,4-cyclohexanediacetic acid; isophthalic acid;5-hydroxyisophthalic acid; terephthalic acid;4,4′-benzophenonedicarboxylic acid; 2,6-naphthalenedicarboxylic acid;and 5-t-butylisophthalic acid, alkali metal salts (Li, Na or K) ofsulpho-5-isophthalic acid, and the C36 fatty acid dimers known under thename Pripol.

These comonomers are commercially available and may be biobased.

The diamine comonomers (different from the monomers of formula V) may bechosen, for example, from: hexamethylenediamine; 1,4-diaminobutane;1,5-diaminopentane; 2-methyl-1,5-diaminopentane;2-methylhexamethylenediamine; 3-methylhexamethylenediamine;2,5-dimethylhexamethylenediamine; 2,2-dimethylpentamethylenediamine;1,7-diaminoheptane, 1,8-diaminooctane; 1,9-diaminononanediamine;2-methyl-1,8-octanediamine, 5-methylnonanediamine, 1,10-diaminodecane;1,11-diaminoundecane; 1,12-diaminododecane; 2,2,4- and2,4,4-trimethylhexamethylenediamine;2,2,7,7-tetramethyloctamethylenediamine; meta-xylylenediamine;para-xylylenediamine; isophoronediamine; 4,4′-diaminodiphenylmethane;4,4′-methylenebis(cyclohexylamine); C2-C16 aliphatic diamines that maybe substituted with one or more alkyl groups, the C36 diaminesoriginating from fatty acid dimers known under the name Priamine;2,5-bis(aminomethyl)furan and 2,5-bis((aminomethyl)tetrahydrofuran;para-phenylenediamine; meta-phenylenediamine; and the ethoxylateddiamines known under the name Jeffamine or Elastamine (polyetherdiaminecomprising ethers of ethylene glycol and/or of propylene glycol and/orof tetramethylene glycol).

These comonomers are commercially available and may be biobased.

The lactam or amino acid comonomers may be chosen, for example, fromcaprolactam, 6-aminohexanoic acid; 5-aminopentanoic acid,7-aminoheptanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid anddodecanolactam.

These comonomers are commercially available and may be biobased.

Several processes for manufacturing the polyamide according to theinvention may be envisaged, as described previously. These processes maybe continuous or batch processes.

A first process proposed by the present invention is a process forpreparing the polyamide according to the invention, which comprises apolycondensation reaction between:

at least one dicarboxylic acid of formula IV below:

at least one diamine of formula V below:H₂N—R—NH₂  (V)with R as defined above.

According to one preferred embodiment of the invention, at least onediamine of formula V is biobased according to standard ASTM D6866.

According to one preferred embodiment of the invention, dicarboxylicacid of formula IV is biobased according to standard ASTM D6866.

This first process is similar in its conditions to the standard processfor preparing polyamide of the type obtained from dicarboxylic acids anddiamines, in particular the process for manufacturing polyamide 66 fromadipic acid and hexamethylenediamine or the process for manufacturingthe polyamide MXD6 by direct amidation starting with molten adipic acidand meta-xylylenediamine. The processes for manufacturing polyamide 66and MXD6 are known to those skilled in the art. The process formanufacturing polyamide of the type obtained from dicarboxylic acids anddiamines generally uses as starting material a salt obtained by mixing,in stoichiometric amount, generally in a solvent such as water, of adiacid with a diamine. Thus, in the manufacture ofpoly(hexamethyleneadipamide), adipic acid is mixed withhexamethylenediamine generally in water to obtainhexamethylenediammonium adipate, which is more commonly known as Nylonsalt or “N Salt”.

Thus, in the manufacture of the polyamide according to the invention,the dicarboxylic acid of formula IV is mixed with the diamine of formulaV, generally in water to obtain a salt of the two monomers. As explainedabove, these monomers may comprise up to 50 mol %, preferably up to 30mol % and even more preferentially up to 15 mol % of other comonomers asdescribed previously.

The salt solution is optionally concentrated by partial or totalevaporation of the water.

The polyamide is obtained by heating at high temperature and highpressure of an aqueous solution of the monomers (for example a saltsolution as described above), or of a liquid comprising the monomers, toevaporate the water and/or the liquid while at the same time avoidingthe formation of a solid phase.

The polymerization medium may also comprise additives such as antifoams,chain limiters (monofunctional molecules capable of reacting with theacid and/or amine functions), branching agents (i.e. molecules bearingat least three functional groups chosen from carboxylic acid and aminegroups), catalysts, stabilizers (with respect to UV, heat or light),matting agents (for instance TiO₂, etc.), lubricants and pigments.

The polycondensation reaction is generally performed at a pressure ofabout 0.5-3.5 MPa (0.5-2.5 MPa) and at a temperature of about 180-320°C. (215-300° C.). The polycondensation is generally continued in themelt at atmospheric or reduced pressure so as to achieve the desireddegree of progress.

The polycondensation product is a molten polymer or prepolymer. At thisstage, the reaction medium may comprise a vapour phase consistingessentially of vapour of the elimination product, in particular water,which may have been formed and/or vaporized.

This product may be subjected to steps for separating out the vapourphase and for finishing in order to achieve the desired degree ofpolycondensation. The separation of the vapour phase may be performed,for example, in a device of cyclone type for a continuous process. Suchdevices are known.

The finishing consists in maintaining the polycondensation product inmolten form, at a pressure in the region of atmospheric pressure or at areduced pressure, for a time that is sufficient to achieve the desireddegree of progress. Such an operation is known to those skilled in theart. The temperature of the finishing step is advantageously greaterthan or equal to 200° C. and in all cases greater than thesolidification temperature of the polymer. The residence time in thefinishing device is preferably greater than or equal to 5 minutes.

In the case of processes that are more suited to the polymerization ofthe polyamide MXD6, the two monomers are introduced into the reactorwithout proceeding via a salification phase: this is then referred to asthe direct amidation process. The reaction in this case is generallyperformed at atmospheric pressure.

The polycondensation product may also undergo a post-condensation stepin solid or liquid phase. This step is known to those skilled in the artand makes it possible to increase the degree of polycondensation to adesired value.

The polyamide obtained via the process of the invention in molten formmay thus be formed directly or may be extruded and granulated, for anoptional post-condensation step and/or for subsequent forming aftermelting.

A second process for preparing the polyamide according to the inventionis a “diester aminolysis” process, i.e. at least one diamine of formulaV as described previously is reacted with at least one diester offormula IV′, preferably a methyl, ethyl, propyl or butyl diester of thecarboxylic acid of formula IV as described previously. A similar processapplied to different monomers is moreover described in the publicationfrom Ulrich Fehrenbacher in Chemie Ingenieur Technik (Polymere) 2009,81, 11, 1829-1835. According to one preferred embodiment of theinvention, at least one diamine of formula V is biobased according tostandard ASTM D6866. According to one preferred embodiment of theinvention, at least one diester of formula IV′ is biobased according tostandard ASTM D6866.

The present invention also envisages another process for preparing thepolyamide according to the invention, the said process comprising thereaction between at least one diamine of formula V as describedpreviously and at least one dinitrile of formula IV″ as describedearlier on in the description. A similar process applied to differentmonomers is moreover described in WO2001/079327. According to onepreferred embodiment of the invention, at least one diamine of formula Vis biobased according to standard ASTM D6866. According to one preferredembodiment of the invention, at least one dinitrile of formula IV″ isbiobased according to standard ASTM D6866.

Lastly, the present invention also provides another process forpreparing the polyamide according to the invention, said processcomprising reacting at least one diamine of formula V as described abovewith at least one acid dichloride of formula IV′″ as described earlieron above in the description, this reaction generally being carried outin solution or by interfacial polymerization. This is a synthesisprocess known to the skilled person and used especially for thesynthesis of aromatic polyamides such as Kevlar®.

The polyamide may be used to make articles by moulding,injection-moulding, injection/blow-moulding, extrusion/blow-moulding,extrusion or spinning. The articles may thus take the form of mouldingsor extrudates, films, yarns, fibres or filaments.

The articles thus obtained have applications in numerous fields such astechnical plastics (motor vehicle, E&E, consumer goods), industrialyarns, the textile industry, packaging, etc.

The present invention also relates to compositions comprising at leastthe polyamide of the invention, and optionally reinforcing fillersand/or various additives.

Such a composition preferentially comprises from 1% to 80% by weight ofthe polyamide according to the invention, relative to the total weightof the composition. This composition may especially comprise other typesof polymer, especially such as thermoplastic polymers.

The composition may also comprise reinforcing or bulking fillers.Reinforcing or bulking fillers are fillers conventionally used formaking polyamide compositions. Mention may be made especially ofreinforcing fibrous fillers, such as glass fibres, carbon fibres ororganic fibres, non-fibrous fillers such as particulate or lamellarfillers and/or exfoliable or non-exfoliable nanofillers, for instancealumina, carbon black, clays, zirconium phosphate, kaolin, calciumcarbonate, copper, diatomaceous earths, graphite, mica, silica, titaniumdioxide, zeolites, talc, wollastonite, polymeric fillers, for instancedimethacrylate particles, glass beads or glass powder.

The composition according to the invention may comprise between 5% and60% by weight of reinforcing or bulking fillers and preferentiallybetween 10% and 40% by weight, relative to the total weight of thecomposition.

The composition according to the invention comprising the polyamide asdefined previously may comprise at least one impact modifier, i.e. acompound that is capable of modifying the impact strength of a polyamidecomposition. These impact modifier compounds preferentially comprisefunctional groups that are reactive with the polyamide. According to theinvention, the term “functional groups that are reactive with thepolyamide” means groups that are capable of reacting or of interactingchemically with the acid or amine functions of the polyamide, especiallyby covalency, ionic or hydrogen interaction or van der Waals bonding.Such reactive groups ensure good dispersion of the impact modifiers inthe polyamide matrix. Good dispersion is generally obtained with impactmodifier particles that have a mean size of between 0.1 and 2 μm in thematrix.

The composition according to the invention may also comprise additivesusually used for the manufacture of polyamide compositions. Thus,mention may be made of lubricants, flame retardants, light and/or heatstabilizers, plasticizers, nucleating agents, UV stabilizers, catalysts,antioxidants, antistatic agents, dyes, matting agents, mouldingadditives or other conventional additives.

These fillers and additives may be added to the modified polyamide viausual means suited to each filler or additive, for instance during thepolymerization or mixed in the melt. The polyamide compositions aregenerally obtained by mixing the various compounds included in thecomposition without heat or in the melt. The process is performed atmore or less high temperature, at more or less high shear depending onthe nature of the various compounds. The compounds may be introducedsimultaneously or successively. An extrusion device in which thematerial is heated, and then melted and subjected to a shear force, andconveyed, is generally used.

It is possible to mix all the compounds in the molten phase in a singleoperation, for example during an extrusion operation. It is possible,for example, to perform a mixing of granules of the polymer materials,to introduce them into the extrusion device in order to melt them and tosubject them to a more or less high shear. According to particularembodiments, premixing, optionally in the melt, of some of the compoundsmay be performed before preparation of the final composition.

The composition according to the invention, when it is prepared using anextrusion device, is preferably conditioned in the form of granules. Thegranules are intended to be formed using processes involving melting toobtain articles. The articles are thus constituted by the composition.According to one common embodiment, the modified polyamide is extrudedin the form of rods, for example in a twin-screw extrusion device, whichare then chopped into granules. The pieces are then made by melting thegranules produced above and feeding the composition in melt form intoforming devices, for example injection-moulding devices.

The composition according to the invention allows the preparation ofarticles obtained by forming the said composition, for example byextrusion, especially extrusion of plates, sheets or films, moulding,especially injection-moulding, rotary moulding, blow-moulding,especially injection/blow-moulding, or spinning. Articles that may bementioned include those used in the motor vehicle or electronics andelectrical industry, for example.

The articles obtained may especially be mouldings, blow-mouldings orextrudates, yarns, fibres, filaments or films.

The polyamide according to the invention has many advantages. First, itis advantageously at least partly biobased, which makes it possible toreduce its environmental footprint. It also has very advantageousmechanical properties, a high molar mass and, depending on the diamineused, it may be semi-crystalline. The polyamide of the invention may,finally, replace the polyamides conventionally used in fields such astechnical plastics (motor vehicle, E&E, consumer goods), industrialyarns, the textile industry, packaging, etc.

The process of the invention also has many advantages. In particular,when it is a process of “salt” type it is very easy to control thestoichiometry between the dicarboxylic acid and the diamine.Furthermore, the process does not generate any degradation products suchas furan, which is a highly toxic product. In addition, the preparationof the polyamide according to the invention may be performed usingindustrial equipment usually used in factories for manufacturingpolyamides of the type obtained from dicarboxylic acids and diamines,especially polyamide 66, and therefore does not require any additionalindustrial investment.

Other details or advantages of the invention will emerge more clearly inthe light of the examples given below.

EXAMPLES

Melting temperature (Tm, and associated enthalpy □Hm), crystallizationtemperature (Tc), and glass transition (Tg) are determined byDifferential Scanning calorimetry (DSC) using a Perkin Elmer Pyris 1,with heating and cooling rate of 10° C./min.

Thermal stability is evaluated by Thermo-Gravimetric Analysis (TGA)under nitrogen using a Perkin Elmer TGA7, by heating a 10 mg sample from40° C. to 600° C. at a heating rate of 10° C./min. Degradationtemperature corresponding to the weight loss of 1%, 3% and 10% arerecorded and respectively named Tdec1%, Tdec3% and Tdec10%.

1H NMR analysis of polyamide is achieved using a Bruker AV500 in1,1,1,3,3,3-Hexafluoro-2-propanol-d2 or D₂SO₄ if deuterated HFIP is nota good solvent.

Amine end-groups (AEG) and carboxylic end-groups (CEG) concentrations(in mmol/kg) are determined by titration. We calculate the averagemolecular weight in number Mn_(−EG) from end-grous concentration byMn_(−EG)=2000000/(AEG+CEG).

Viscosity Index (VI, in mL/g) is measured in formic acid as a solventaccording to ISO307.

Example 1: Preparation of a Polyamide from 2,5-Furandicarboxylic Acid(FDCA) and Hexamethylenediamine

A salt of 2,5-furandicarboxylic acid (FDCA) and of hexamethylenediamineis prepared by adding 2 g of FDCA (0.0128 mol) to 4.59 g of aqueous32.5% hexamethylenediamine solution (0.0128 mol). Exothermicity isproduced during the salification, and the reaction medium is thenmaintained at 50° C. for 2 hours and becomes perfectly clear. The saltis recovered and then analysed by thermogravimetric analysis coupled toan infrared detector: this involves heating the salt at 10° C./min. Asubstantial evolution of CO₂ and of furan is detected at and above 245°C., i.e. during the melting of the salt 6FDCA, which is a sign ofdegradation of the 2,5-furandicarboxylic acid units. It is therefore notpossible to prepare polyamides of high molecular mass via this route.

Examples 2: Preparation of Polyamides from THFDCA and Diamines

A salt of hexamethylenediamine and of 2,5-tetrahydrofurandicarboxylicacid (monomer noted THFDCA or TF) is prepared by mixing at roomtemperature the monomers in stoichiometric amount (2 g of TF (0.0125mol) and 1.45 g of hexamethylenediamine) in ethanol. The reaction mediumis heated at 70° C. for 2 hours. After cooling, the dry salt isrecovered by filtration and drying. This is the salt named 6TF.

A salt of 1,10-diaminodecane and of 2,5-tetrahydrofurandicarboxylic acidis prepared by mixing at room temperature the monomers in stoichiometricamount (2 g of TF (0.0125 mol) and 2.153 g of 1,10-diaminodecane) at 20%in water. The reaction medium is heated at 70° C. for 2 hours. Aftercooling, the dry salt is recovered by filtration and drying. This is thesalt named 10TF.

Each salt is heated above its melting point and the amidation reactiontakes place. The polyamides obtained have satisfactory thermalcharacteristics.

Example 3: Synthesis of Homopolyamides by Diester Route

Dimethyl 2,5-tetrahydrofuranoate cis/trans 90/10 (named dmTHFDCAcis/trans 90/10) is synthesized as follows. In a 3 L flask equipped witha reflux condenser and a thermometer furan-2,5-dicarboxylic acid (FDCA)(200 g, 1.28 mol), H₂SO₄ (98%, 90 ml) were dissolved in 1.4 L ofmethanol. The reaction mixture was stirred under reflux for 22 h. Aftercooling to R.T, the mixture was concentrated in vacuum and the residuewas dissolved in 1.5 L of DCM. The obtained solution was washed by water(2×400 ml), saturated NaHCO₃ solution (2×300 ml), and brine (2×300 ml).The organic layer was dried and concentrated in vacuum to give 203 g ofwhite solid (86% yield), and the solid was used for next step withoutfurther purification.

In a 5 L Parr reactor the white solid obtained (250 g, 1.36 mol), Pd/C(10%, 25.0 g) were suspended in 2.5 L of methanol. The reaction mixturewas stirred at 50° C. under an atmosphere of hydrogen at 20 bar, andmonitored by LC/MS. When the reaction is completed the mixture wasfiltered through silica gel and the filtrate was concentrated in vacuoand distilled under reduced pressure to give 228 g of colorless oil (85°C./50 Pa, 89% yield).

2,5-tetrahydrofurandicarboxylic acid cis/trans 90/10 (named THFDCA) issynthesized as follows. In a 50 ml round-bottomed flask equipped with areflux condenser the dmTHFDCA (1 g, 5.3 mmol) was dissolved in 1 ml ofTFA and 5 ml of water. The mixture was heated at 100° C. and monitoredby LC-MS. When the reaction is completed the mixture was concentratedunder vacuum to give 0.78 g of white solid (92% yield). If necessary theproduct would be further purified by recrystallization.

We synthesize polyamides starting from dimethyl 2,5-tetrahydrofuranoatecis/trans 90/10 (named dmTHFDCA cis/trans 90/10) and a stoichiometricamount of a diamine. Diamines evaluated are: hexamethylene diamine,1,10-diaminodecane, 1,4-diaminobutane, meta-xylylene diamine, isophoronediamine, 1,3-bis(aminomethyl)cyclohexane and4,4′-Methylenebis(2-methylcyclohexylamine) mixture of isomers allsupplied by Sigma-Aldrich.

The same method is used to synthesize all the different polyamides. Hereis described the method used for the synthesis of PA 10TF.

In a glass reactor is introduced 16,002 g of dmTHFDCA cis/trans 90/10prepared by ourselves according to the procedure described (purity 98%,0.083 mol) and 14,666 g of 1,10-diaminodecane (purity 98%, 0.083 mol).Nitrogen blanket is then used and the monomers are stirred using amechanical stirrer. The glass reactor is immersed in a heating bathregulated at 80° C. and then heated to final temperature (230° C.) withheating rate of 1.5° C./min. Methanol produced during the reactionbetween the diester and the diamine (beginning of the appearance ofboiling in the reaction mixture when bath is at 90° C.) is removed bydistillation. When the reactor is at final temperature, pressure in theglass reactor is decreased to about 60 mbar and maintained under vacuumduring 30 minutes. Nitrogen is introduced to come back to atmosphericpressure, stirring is stopped and the glass reactor removed from heatingbath to cool the reaction mixture. A yellowish transparent solid isrecovered.

1H NMR analysis in deuterated HFIP confirms the reaction between THFDCAand 1,10-diaminodecane. Thermal properties analysis shows that the PA10TF_(cis/trans90/10) is an amorphous solid with Tg=47° C. and has avery good thermal stability up to more than 280° C., giving a broadprocessing window between Tg and Tdec1%.

A similar method is used for the synthesis of polyamides with dmTHFDCAcis/trans 90/10 and various diamines. Thermal properties of thehomopolyamides are reported in Table 1.

In any case, all homopolyamides are all yellowish transparent amorphoussolids with Tg up to 162° C., depending on the rigidity of the diamineused. They can compete with other existing commercial amorphouspolyamides.

TABLE 1 Properties of homopolyamides synthesized using dmTHFDCAcis/trans 90/10. Tg Tdec1% Tdec3% Tdec10% Diamine ° C. ° C. ° C. ° C. PA4TF 1,4-diamino butane 92 291 327 362 PA 6TF Hexamethylene diamine 65283 342 381 PA 10TF 1,10 diamino decane 47 285 351 393 PA 1,3-BAMCTF1,3-bis(aminomethyl) 133 296 336 377 cyclohexane mixture of isomers PAMXDTF Meta-xylylene diamine 117 306 335 355 PA ISOTF Isophorone diamine143 N.D. N.D. N.D. PA MBMCTF 4,4′-Methylenebis(2- 162 N.D. N.D. N.D.methylcyclohexylamine) mixture of isomers

Example 4: Synthesis of PA 66/6TF Copolyamides Using Salt Route

We use a sample of THFDCA cis/trans 95/5 for the synthesis of PA 66/6TF95/5, 90/10 and 80/20 mol/mol. Polymerization of theses copolyamides isachieved using a classical PA 66 synthesis process: we prepare anaqueous salt composed with diacids mixtures (adipic acid and THFDCA) andhexamethylene diamine at a concentration of 52 wt.-% in water and 70°C., we concentrate the aqueous salt up to 70 wt.-% under atmosphericpressure by removing water by heating, we then heat the reactor under17.5 bar pressure (distillation of water under pressure), wedepressurize to atmospheric pressure when the temperature of thereaction mixture reaches 250° C. and we finish the reaction at 272° C.during 30 min at atmospheric pressure. The copolyamides are extrudedfrom the reactor under pressure, cooled in a cold water bath to get astrand and then pelletized.

For PA 66/6TF 95/5 mol/mol, we started the reaction by mixing 142.62 g(0.544 mol) of Nylon 66 salt (stoichiometric salt of adipic acid andhexamethylene diamine), 11.78 g (0.0330 mol) of hexamethylene diamine at32.5% in water, 4.57 g (0.029 mol) of THFDCA, 130 g of water and 2 g ofan anti-foaming agent.

For PA 66/6TF 90/10 mol/mol, we started the reaction by mixing 134.48 g(0.513 mol) of Nylon 66 salt (stoichiometric salt of adipic acid andhexamethylene diamine), 20.50 g (0.057 mol) of hexamethylene diamine at32.5% in water, 9.12 g (0.057 mol) of THFDCA, 124 g of water and 2 g ofan anti-foaming agent.

For PA 66/6TF 80/20 mol/mol, we started the reaction by mixing 118.96 g(0.453 mol) of Nylon 66 salt (stoichiometric salt of adipic acid andhexamethylene diamine), 40.55 g (0.113 mol) of hexamethylene diamine at32.5% in water, 18.13 g (0.113 mol) of THFDCA, 109 g of water and 2 g ofan anti-foaming agent.

Properties of these copolyamides are reported in Table 2.

The more THFDCA is included in PA 66 chains, the lower the Tm, Hm andTc. We generally use comonomers to decrease the crystallization kineticsto get molded part having a better surface aspect or for fiber spinning.As a comparison, a PA 66/6I 80/20 mol/mol (I=isophthalic acid)synthesized using the same method 80/20 mol/mol has the followingthermal properties: Tm=240° C., Tc=193° C. and Tg=76° C. PA 66copolyamides having THFDCA or isophthalic acid as comonomers in similarcontent exhibit similar crystallization kinetics but THFDCA doesn'tincrease Tg.

We observed in our conditions that the cis/trans ratio of THFDCA changedfrom 95/5 to 82/18 mol/mol after the synthesis of PA 66/6TF 80/20mol/mol.

TABLE 2 Properties of copolyamides synthesized using THFDCA cis/trans95/5. CEG AEG meq/ meq/ Mn_(-EG) IV Tm Tc Tg* kg kg g/mol mL/g ° C. Hm °C. ° C. PA 66 80 50 15390 129 262 65 220 67 PA 66/6TF 58.5 109 11940105.9 255 63 211 69 95/5 mol/ mol PA 66/6TF 74.6 105 11140 97.7 250 56206 68 90/10 mol/ mol PA 66/6TF 85 159.9 8170 74.1 237 45 188 66 80/20mol/ mol *Determined at 40° C./min

Pellets of copolyamides are then dried during 16 h at 90° C. undervacuum before being submitted to injection molding to get specimens(bars 90×13×1.6 mm³) using a micro-extruder DSM MIDI 2000 with barreltemperature at 280° C. and mould temperature at 70° C.

Water absorption (RH100, 23° C., saturation) of the copolyamides isanalyzed by placing the specimens in water at room temperature and byfollowing the weight of the specimens until no change in weight isobserved. Water absorption is determined by calculating (mf−mi)/mi, withmi=initial weight of the specimen before the test (dry), mf=final weightwhen the specimen is saturated with water.

PA 66/6THF 100/0, 95/5, 90/10 and 80/20 mol/mol respectively absorb 8.5wt.-%, 9.9 wt.-%, 11 wt.-%, 14 wt.-% of water. It is higher than waterabsorption obtain with isophthalic acid as a comonomer. These copolymerswould be interesting to increase the moisture absorption of textilefiber to bring higher comfort.

Example 5: Synthesis of Polyphthalamide Copolyamide Using Salt Route

We synthesized PA 6T/6TF 50/50 mol/mol and PA 10T/10TF 60/40 mol/molusing an aqueous salt route. We use a sample of THFDCA cis/trans 95/5for these syntheses.

Polymerization of theses copolyamides is achieved using a classical PA66 synthesis process with a few modifications: we prepare an aqueoussalt composed with diacids mixtures (terephthalic acid and THFDCA) anddiamine at a concentration of 52 wt.-% in water and 70° C., we close thereactor and we heat the reactor under 17.5 bar pressure (distillation ofwater under pressure), we depressurize to atmospheric pressure when thetemperature of the reaction mixture reach 260° C. and we finish thereaction at 290° C. during 10 min at atmospheric pressure. Thecopolyamides are extruded from the reactor, cooled in a cold water bathto get a strand and then pelletized.

For PA 6T/6TF 50/50 mol/mol, we started the reaction by mixing 49.89 g(0.1767 mol) of Nylon 6T salt (stoichiometric salt of terephthalic acidand hexamethylene diamine), 66.61 g (0.1768 mol) of hexamethylenediamine at 30.85% in water, 28.34 g (0.177 mol) of THFDCA, 43.9 g ofwater and 2 g of an anti-foaming agent.

For PA 10T/10TF 60/40 mol/mol, we started the reaction by mixing 28.61 g(0.172 mol) of terephthalic acid, 50.39 g (0.287 mol) of1,10-diaminodecane (purity=98%), 18.39 g (0.115 mol) of THFDCA, 86.62 gof water and 2 g of an anti-foaming agent.

TABLE 3 Properties of copolyamides synthesized using THFDCA cis/trans95/5. Tm Tc Tg* ° C. Hm ° C. ° C. PA 6T/6TF 50/50 mol/mol 273 10 231 104PA 10T/10TF 60/40 mol/mol 241/256 29 222 84 *Determined at 10° C./min

THFDCA can be used in polyphthalamide to modulate the thermal propertiesof PA 6T and PA 10T.

What is claimed is:
 1. A polyamide comprising the repeating unit offormula I below:

in which R represents a covalent bond or a divalent hydrocarbon-basedgroup chosen from saturated or unsaturated aliphatics, saturated orunsaturated cycloaliphatics, aromatics, arylaliphatics andalkylaromatics.
 2. The polyamide according to claim 1, in which R ischosen from linear or branched alkyl groups having from 1 to 36 carbonatoms.
 3. The polyamide according to claim 2, in which R is a linearalkyl group having from 4 to 14 carbon atoms.
 4. The polyamide accordingto claim 1, in which R is chosen from: —(CH₂)₄—, —(CH₂)₅—, —(CH₂)₆—,—(CH₂)—CH(CH₃)—(CH₂)₃—, —(CH₂)₁₀— and —(CH₂)₁₂—.
 5. The polyamideaccording to claim 1, in which R is a divalent aromatichydrocarbon-based group comprising from 6 to 18 carbon atoms.
 6. Thepolyamide according to claim 5, in which R is 1,4-benzene, 1,3-benzeneor —(CH₂)-Ph-(CH₂)— in positions 1,3 and 1,4.
 7. The polyamide accordingto claim 1, wherein said polyamide is a homopolyamide consistingentirely of the repeating unit of formula I.
 8. The polyamide accordingto claim 1, wherein said polyamide is a copolymer comprising otherrepeating units different from the unit of formula I.
 9. The polyamideaccording to claim 8, wherein the repeating units different from theunit of formula I comprise comonomers selected from dicarboxylic acids,diamines, amino acids and/or lactams.
 10. The polyamide according toclaim 8, wherein said polyamide is a copolymer chosen from the groupconsisting of: PA 6T/6TF, PA10T/10TF, PA6T/6TF/66, PA66/6TF, PA12T/12TFand PA610/6TF.
 11. An article obtained from the polyamide according toclaim 1, the said article being a molding or extrudate, yarn, fiber,filament, or film.
 12. A composition comprising at least the polyamideaccording to claim 1, and optionally reinforcing fillers and/or variousadditives.